You’re not supposed to remove your hat in any public space where you do not expect to sit down for an extended length of time. For example, you remove your hat when in a restaurant or a church, but not in a post office, store, bus station or airport terminal (never mind that in the last two instances you may very well be sitting there for a long time ).
As for how you cut your meat… well, my take on that is that anyone watching you eat that intently is ill-mannered in themselves. Most table manners are to insure that 1) you don’t sicken your fellow diners, or 2) you don’t jumble up the serving so badly that it creates discomfort for your fellow diners or the servers. If you use your dessert fork for the seafood course, you will be left trying to eat your dessert with that teeny seafood fork–or your hostess will have to get up and go find another fork for you. See? It’s just a matter of making things go smoothly so people can concentrate on the company and not on the food.
I’d like to mention that I briefly dated a very good-looking man with a decent sense of humor and a beautiful singing voice because he refused to open car doors for me. Just think of all the great sex he missed out on!
Let me address the class issue: you should adjust your manners to fit the company you’re in. My sister’s mother-in-law giving my sister and I a lecture in her home for saying “taties” rather than “potatoes” was one of the most egregious displays of bad manners that I was ever subjected to. My family is working class/farmers. Everybody sits in the kitchen; the parlor is for formal occasions or for the preacher. So if you come to my house, it’s not bad manners for me to entertain you in the kitchen. If your custom is that everybody sits in the living room or family room and that only family goes into the kitchen, it would be bad manners of me to insist on sitting in the kitchen. In my culture, if you come to my home, I would never think not to offer you something to drink or eat. You will accept at least a soda or cup of coffee, even if you don’t drink it. To decline would be to imply that you were somehow “above” what I was offering you.
Eh, I’ve rambled, but my point is that one adjusts one’s manners to fit the company.